iRedMail-0.8.3 and earlier versions have this issue. Here's fix for OpenLDAP backend:

- In /etc/postfix/ldap/sender_bcc_maps_user.cf, replace "(mail=%s)" by "(|(mail=%s)(&(enabledService=shadowaddress)(shadowAddress=%s)))" in parameter "query_filter =". The final LDAP filter looks like below:

To avoid too many SQL lookups in Postfix, i prefer fixing it with iRedAdmin-Pro:

- While adding new alias domain for domain 'example.com', iRedAdmin-Pro-MySQL or iRedAdmin-Pro-PGSQL will insert new records in SQL tables (vmail.sender_bcc_domain, vmail.recipient_bcc_domain) if domain 'example.com' has bcc settings, or users under 'example.com' have bcc settings (vmail.sender_bcc_user, vmail.recipient_bcc_user).

- Perform opposite process while removing alias domain.

This fix will be available in next release of iRedAdmin-Pro-MySQL and iRedAdmin-Pro-PGSQL.

I think I've found a problem with monitoring of incoming & outgoing mails through BCC. When I configure this per user, it works for the main e-mail address, but not for all mail aliases of this user. I didn't test this BCC feature with aliases at domain level, so maybe there is the same issue?